Residue on Ignition Test Procedure as per BP & USP

Explore the detailed Residue on Ignition Test Procedure following BP & USP guidelines. Enhance your laboratory practices with our expert insights.

STP – Residue on Ignition

1.0     Objective

    • The objective of this GTP is to describe the procedure to be used for performing residue on ignition test.

2.0     Principle/Reaction

    • It is a quantitative measuring technique used to find out presence of inorganic impurities.
    • It can be measured in terms of % w/w of the substance being examined.

3.0     Requirements for Residue on Ignition (ROI)Residue on Ignition - STP

    • As per BP/USP
    • Silica or platinum crucible
    • Sulphuric acid
    • Muffle furnace
    • Desiccator
    • Pipette
    • Analytical balance

4.0     Test Procedure for Residue on Ignition as per BP/ Ph.Eur

    • Method I – For Residue on Ignition

    • Heat a platinum dish to redness for 10 minutes, allow to cool in a desiccator and weigh.
    • Unless otherwise specified in the monograph, place 1 g of the substance being examined in the dish, moisten with sulphuric acid, ignite  gently, again moisten with sulphuric acid and ignite at about 800°C.
    • Cool, weigh again, ignite for 15 minutes and repeat this procedure until two successive weighing do not differ by more than 0.5 mg.

    • Method I – For Residue on Ignition

    • Ignite a suitable crucible (for example, silica, platinum, porcelain or quartz) at 600 ±  50° C for 30 min,
    • Allow to cool in a desiccator over silica gel or other suitable  desiccant and weigh.
    • Place the prescribed amount of the substance to be examined in the crucible and weigh.
    • Moisten the substance to be examined with a small amount of sulphuric acid (usually 1 ml) and heat gently at as low a temperature as practicable until the sample is thoroughly charred.
    • After cooling, moisten the residue with a small amount of sulphuric acid (1 ml unless specified in individual standards test procedure), heat gently until white fumes are no longer evolved and ignite at 600 ± 50° C until the residue is completely  incinerated.
    • Ensure that flames are not produced at any time during the procedure.
    • Allow the crucible to cool in a desiccator over silica gel, weigh it again and calculate the percentage of residue.
    • If the amount of the residue so obtained exceeds the prescribed limit, repeat the moistening with sulphuric acid and ignition, as previously, for 30 minutes periods until 2 consecutive weights do not differ by more than 0.5 mg or until the percentage of residue complies with the prescribed limit.

5.0     Test Procedure for Residue on Ignition as per USP

    • Weigh accurately 1 to 2 g of the substance, or the amount specified in the individual monograph, in a suitable crucible that previously has been ignited, cooled, and weighed.
    • Heat, gently at first, until the substance is thoroughly charred, cool, then, unless otherwise directed in the individual monograph.
    • Moisten the residue with 1 ml of sulfuric acid, heat gently until white fumes no longer are evolved, and ignite at 600 ± 50°C, unless another temperature is specified in the individual monograph, until the carbon is consumed.
    • Cool in a desiccator, weigh, and calculate the percentage of residue.
    • If the amount of the residue so obtained exceeds the limit specified in the individual monograph.
    • Again moisten the residue with 1 ml of sulfuric acid, heat and ignite as before, and again calculate the percentage of residue.
    • Unless otherwise specified, continue the ignition until constant weight is attained or until the percentage of residue complies with the limit in the individual monograph.
    • Conduct the ignition in a well-ventilated hood, but protected from air currents, and at as low a temperature as is possible to effect the complete combustion of the carbon.
    • A muffle furnace may be used, if desired, and its use is recommended for the final ignition at 600 ± 50°C.
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